Honda Motor Co., Ltd.

Daido Steel Co., Ltd.

Nippon Steel Corporation

Isamu Saito

Shinichiro Kato

Takahiro Miyazaki

Takashi Kano

Yoshihiro Takitani

Makoto Hobo

Keiichiro Kamiya

Tatsuya Hasegawa

Hideki Matsuda

Motoki Takasuga

Yusuke Miyakoshi

Masashi Kawakami

A rolled steel material for fracture splitting connecting rods consists of, C: 0.30 to 0.40%, Si: 0.60 to 1.00%, Mn: 0.50 to 1.00%, P: 0.04 to 0.07%, S: 0.04 to 0.13%, Cr: 0.10 to 0.30%, V: 0.05 to 0.14%, Ti: more than 0.15% to 0.20% or less, N: 0.002 to 0.020%, and optionally may contain Cu, Ni, Mo, Pb, Te, Ca, and Bi, with the balance being Fe and impurities. fn1, defined by Formula (1), ranges from 0.65 to 0.80. Relative to the V content in the steel material, a V content in coarse precipitates having a particle size of 200 nm or more is 70% or less, and relative to the Ti content in the steel material, a Ti content in the coarse precipitates is 50% or more.1=C+Si/10+Mn/5+5Cr/22+(Cu+Ni)/20+Mo/2+33V/20&#x2212;5S/7&#x2003;&#x2003;(1)

Rolled steel material for fracture splitting connecting rod

A nitrocarburized crankshaft member made of a steel that includes C in an amount by weight of 0.25 to 0.32% as a required element and an optional element that may be included, and Fe and inevitable impurities in a remaining portion. The steel-made crankshaft member mainly includes ferrite and perlite, wherein at least a portion of the steel surface thereof having a ferrite surface area of 50% or greater is imparted with a nitrocarburized hard layer. The nitrocarburized hard layer includes a surface compound layer suppressed to a thickness of 10 to 35 &#x3bc;m, and a nitrogen diffusion zone below the surface compound layer having a diffusion depth of 700 &#x3bc;m or greater. The steel includes C, Si, Mn, Cu, Ni, and Cr as the required elements and Mo, N, s-Al, and Ti as the optional elements.

Nitrocarburized crankshaft member and steel for nitrocarburized crankshafts

The invention relates to a crankshaft member having high fatigue strength and good bending correctability, and its method of manufacture. The steel made crankshaft member mainly consists of a two-phase structure of ferrite and perlite. The steel includes C, Ni, Mn, and Cr as required elements and Si, Cu, Mo, Ti, V, Nb, Ca, and S as optional elements that may be included, in the amounts of C within the range of 0.20 to 0.50 wt %, Si within the range of 0 to 0.6 wt %, Mn within the range of 0.5 to 1.5 wt %, Cu within the range of 0 to 0.7 wt %, Ni within the range of 0.05 to 1.5 wt %, Cr within the range of 0.05 to 0.45 wt %, and Mo within the range of 0 to 0.5 wt % to satisfy the condition 115&#x2267;70C+8Si+23Mn+11Cu+128Cr+83Mo&#x2267;50. A portion of the member surface is provided at least with a hard nitride layer having an average hardness within the range of 300 to 450 HV. Lamellar spacing of the perlite is 0.3 &#x3bc;m or less.

Manufacturing method for a crankshaft member

Growing community of inventors

Saitama-ken, Japan

Isamu Saito